Every downhole drilling motor assembly includes a drilling motor and a drill bit. Where a moineau-style motor, having a rotor and stator, is used; there is also provided a drive shaft and a bearing assembly. The drive shaft converts eccentric motion of the moineau-style motor to concentric rotation. The bearing assembly ensures that the transition from eccentric rotation to concentric rotation is smooth and does not adversely affect operation of the drill bit.
During drill out operations, cement and other foreign material is drilled out of well casing. When drilling, a layer of debris, is unavoidably left on the interior casing wall. This debris needs to be cleaned off so that various equipment, which is used in the casing bore, can be anchored or removed. A separate scraper run is, therefore, conducted, in which a casing scraper is used to scrape the interior casing wall bare of any debris.